Multi-stage axial compressor



y 23, 1954 A. B. MCKENZIE 3,142,438

MULTI-STAGE AXIAL COMPRESSOR Filed April 12, 1962 3 Sheets-Sheet 1 Inuenlor MM hey awzw fiiwawzww A ltorneys July 28, 1964 A. B. M KENZIEMULTI-STAGE AXIAL COMPRESSOR 3 Sheets-Sheet 2 Filed April 12, 1962 July28, 1964 A. B. M KENZIE 3,142,438

MULTI-STAGE AXIAL COMPRESSOR Filed April 12, 1962 35116618-511881'. 3

A llorn e ys United States Patent 3,142,438 MULTI-STAGE AXIAL COMPRESSORArchibald Bathgate McKenzie, Littleover, England, assignor toRolls-Royce Limited, Derby, England, a company of Great Britain FiledApr. 12, 1962, Ser. No. 186,988 Claims priority, application GreatBritain Apr. 21, 1961 6 Claims. (Cl. 230122) This invention concerns amulti-stage axial compres sor, e.g. for a gas turbine engine.

Multi-stage axial compressors are known which have a bleed air passagethrough which some of the air compressed by the compressor may be bledfrom one of the stages of the compressor, the said stage having statorblades whose platforms have radially extending apertures through whichsome of the said compressed air may pass to the bleed air passage. Thisarrangement, however, is unsatisfactory if it is required to bleed largequantities of the said compressed air into the bleed air passage bothbecause it may not be possible to make the total area of the saidapertures sufficiently large and because the bleeding of largequantities of compressed air through these apertures may involve seriousaerodynamic losses.

According therefore to the present invention, there is provided amulti-stage axial compressor having a bleed air passage through whichsome of the air compressed by the compressor may be bled from one of thestages of the compressor, the said stage having stator blades each ofwhose platforms is provided with at least one surface which is soinclined with respect to the axis of the compressor as to direct some ofthe said compressed air radially outwardly and in a downstream directiontowards the bleed air passage.

Preferably the downstream end of each said inclined surface is disposedradially outwardly of the platforms of the stator blades of the adjacentstage or stages of the compressor.

Preferably the compressor, on the downstream side of the stator bladesof the said stage, has a wall having an apertured portion whichcommunicates with the bleed air passage and the said inclined surfacesbeing adapted to direct some of the said compressed air through saidapertured portion.

Each said inclined surface may be inclined at an angle of substantially40 to 50 to the longitudinal axis of the compressor.

The compressor may, if desired, have a casing having a wall which isinclined radially outwardly in a downstream direction, the stator bladesof the said stage being mounted in the casing so that their platformsextend parallel to said wall.

The invention also comprises a gas turbine engine provided with acompressor as set forth above.

Additionally the invention comprises an aircraft provided with such agas turbine engine, the bleed air passage being arranged to supplycompressed air to blown flaps on the aircraft.

The invention is illustrated, merely by way of example, in theaccompanying drawings in which:

FIGURE 1 is a broken away axial section of part of a multi-stage axialcompressor according to the present invention,

FIGURE 2 is broken away section taken on the line 22 of FIGURE 1,

FIGURE 3 is a broken away section taken on the line 3-3 of FIGURE 2,

FIGURE 4 is a broken away axial section of part of another multi-stageaxial compressor according to the present invention,

FIGURE 5 is a broken away section showing part of the structure ofFIGURE 4 on a larger scale, and

FIGURE 6 is a broken away view taken in the direction of the arrow 6 ofFIGURE 5.

Referring to FIGURES 1-3 of the drawings, a gas turbine engine (notshown) for use on an aircraft (not shown) comprises a multi-stage axialcompressor 10 having compressor casing means 11. The compressor casingmeans 11 is made up of a number of wall members including annularU-section, wall members 12, 13, 14.

The wall member 13 has radially outwardly extending annular walls 15, 16which are respectively secured by bolts 17, 18 to radially outwardlyextending annular walls 20, 21 of the wall members 12, 14 respectively.The wall member 13 is also provided with a radially inwardly extendingannular wall 22 which is secured to the wall 21 by bolts 23.

The walls 21, 22 are formed with a plurality of aligned, angularlyspaced apart elongated slots 24, 25 respectively.

The compressor 10 includes regularly axially spaced fifth stage statorblades 26, sixth stage rotor blades 27, sixth stage stator blades 28,seventh stage rotor blades 29, and seventh stage stator blades 30. Allof these blades 26 to 30 have a conventional straight-edged aerofoilconfiguration, and all the rotor blades 27, 29 are completely shroudedby the compressor casing means 11.

The sixth stage stator blades 28 extend radially outwardly across ableed passage generally denoted by the reference numeral 36, and haveintegral platforms 32 opposite ends of which are mounted in the walls20, 22. The platforms 32 have internal surfaces 33 which are inclined atan angle of 40 to 50 to the longitudinal axis of the compressor 10 andwhich together form a fluid-tight radially inwardly facing surface ofthe bleed air passage. The downstream ends of the inclined surfaces 33are disposed radially outwardly of the platforms 34, 35 of the statorblades 26, 30 of the adjacent stages of the compressor.

The main fluid duct of the compressor is thus bounded by the innersurfaces of a first section of the compressor casing means, comprisingthe platforms 34 and the wall member 12; a second section axially spacedfrom the first section and comprising the annular wall 22, the platforms35 and the wall member 14; and an intermediate section extending betweenthe first and second sections and comprising the platforms 32. The innersurface of the first section has a downstream end, formed by part of thewall member 12, which is aligned axially of the compressor with theinner surface of the upstream end of the second section, formed by theannular wall 22. Furthermore, the inner surface of the intermediatesection comprising the surfaces 33 diverges outwardly from thedownstream end of the inner surface of the first section towards and inradially outwardly spaced relationship to the upstream end of the secondsection, the inner surface of the intermediate section and the upstreamend of the second section defining an annular space therebetween.

The inclined surfaces 33 are adapted to direct some of the air which hasbeen compressed by the compressor radially outwardly and in a downstreamdirection so that this air will flow smoothly through the elongatedslots 24, 25 and the bleed air passage 36.

The slots 24, 25 (see FIGURE 3) have inwardly inclined Walls, the ribs37 which are formed between the slots 25 being smoothly rounded at theirupstream ends to reduce pressure losses.

Means (not shown) may be provided for closing the slots 24, 25 (or,alternatively, for preventing flow through the bleed air passage 36)whenever it is no longer necessary to bleed air from the compressor 10.

It will be appreciated that the construction described above enableslarge quantities of compressed air to be 3 withdrawn through the slots24, 25 and into the bleed air passage 36. This large quantity ofcompressed air may, for example, be used for the operation of blownflaps on the said aircraft.

In FIGURES 46 there is shown a modified multistage axial compressoraccording to the present invention having a casing 40. Within the casing40 there are mounted inner wall members 41, 42, the inner wall member 41carrying fourth and fifth stage stator blades 43, 44 respectively andthe inner wall member 42 carrying seventh stage stator blades 45.

The casing 40 has a radially outwardly extending projection 46. Theprojection 46 has an axially extending wall 47 and inclined upstream anddownstream walls 48, 49 respectively, the wall 48 being radiallyoutwardly inclined in a downstream direction.

Sixth stage stator blades 50 are mounted in the casing 40 and haveplatforms 51 which extend parallel to the wall 48. The platforms 51 haveinternal surfaces 52 which are inclined at an angle of about 45 to thelongitudinal axis of the compressor. The downstream ends of the inclinedsurfaces 52 are disposed radially outwardly of the platforms of thestator blades 44, 45 of the adjacent stages of the compressor.

The wall 49 has angularly spaced apart elongated slots 53 therein. Theinclined surfaces 52 are adapted to direct some of the air compressed bythe compressor radially outwardly and in a downstream direction so thatthis air will flow smoothly through the elongated slots 53 and so to ableed air passage 54.

I claim:

1. in a multi-stage axial compressor suitable for intermittent bleedingof compressed air therefrom and having a longitudinal axis, a main fluidduct, and easing means for said main fluid duct, said casing meanscomprising first and second axially spaced sections and an intermediatesection extending between said first and second sections, each of saidsections having an inner surface which forms an outer boundary wall of arespective axial portion of said main fluid duct, the inner surface ofsaid first section having a downstream end, and the inner surface ofsaid second section having an upstream end which is aligned axially ofthe compressor with the downstream end of the inner surface of saidfirst section, the inner surface of said intermediate section beingfluid tight and diverging outwardly relatively to the inner surfaces ofthe first and second sections from the downstream end of the innersurface of said first section towards and in radially outwardly spacedrelationship to the upstream end of said second section, the innersurface of said intermediate section and the upstream end of said secondsection defining an annular space therebetween, said casing means beingprovided with duct means in fluid flow communication with said annularspace for bleeding compressed air from said main fluid duct, theimprovement comprising a plurality of angularly arranged stator bladesprovided in said intermediate section, each of the stator bladescarrying at its radially outer end a platform formed integrallytherewith and having a radially inwardly facing surface, the radiallyinwardly facing surfaces of said platforms of said stator bladestogether forming said fluid tight inner surface of said intermediatesection.

2. A multi-stage axial compressor as claimed in claim 1, including aplurality of regularly axially spaced, bladed, alternate rotor andstator stages, all the individual blades of said stages having aconventional straight-edged aerofoil configuration.

3. A multi-stage axial compressor as claimed in claim 2, in which allthe blades of said rotor stages are completely shrouded by said firstand second sections of the casing means.

4. A multi-stage axial compressor suitable for intermittent bleeding ofcompressed air therefrom, and having a compressor casing, a bleed airpassage for bleeding compressed air from said compressor casing, saidbleed air passage having a radially inwardly facing surface whichextends outwardly of said compressor casing, a plurality of regularlyaxially spaced, alternate rotor and stator stages within said compressorcasing, each stage comprising a plurality of angularly arranged blades,the blades of one of said stator stages extending radially outwardly ofthe compressor casing into the bleed air passage, each of said lastmentioned blades carrying at its radially outer end a platform formedintegrally therewith, the platforms together forming said radiallyinwardly facing surface of the bleed air passage, all the blades of saidstages having a conventional straightedged aerofoil configuration, andall the blades of said rotor stages being completely shrouded by saidcompressor casing, whereby when no compressed air is bled through thebleed air passage, the compressor operates efficiently.

5. A compressor as claimed in claim 4 in which said compressor casingcomprises first and second axially spaced sections extending on axiallyopposite sides of said bleed air passage, each of said sections havingan inner surface, the inner surface of said first section having adownstream end, and the inner surface of said second section having anupstream end which is aligned axially of the compressor with thedownstream end of the inner surface of said first section, said radiallyinwardly facing surface of the bleed air passage being fluid tight anddiverging outwardly relatively to the inner surfaces of the first] andsecond sections from the downstream end of the inner surface of saidfirst section towards and in radially outwardly spaced relationship tothe upstream end of said second section, said radially inwardly facingsurface of the bleed air passage and the upstream end of said secondsection defining an annular space therebetween through which compressedair bled from the compressor can flow.

6. A compressor as claimed in claim 4 in which said radially inwardlyfacing surface is inclined at an angle of substantially 40 to to thelongitudinal axis of the compressor.

References Cited in the file of this patent UNITED STATES PATENTS1,447,554 Jones Mar. 6, 1923 2,520,697 Smith Aug. 29, 1950 2,614,799Judson et al. Oct. 21, 1952 2,650,060 Stalker Aug. 25, 1953 2,678,537Stalker May 18, 1954 2,702,157 Stalker Feb. 15, 1955 FOREIGN PATENTS889,506 Germany Sept. 10, 1953 920,732 France Ian. 4, 1947 1,012,339France Apr. 16, 1952 1,068,638 France Feb. 10, 1954 1,099,669 FranceMar. 23, 1955 1,136,881 France Jan. 7, 1957

1. IN A MULTI-STAGE AXIAL COMPRESSOR SUITABLE FOR INTERMITTENT BLEEDINGOF COMPRESSED AIR THEREFROM AND HAVING A LONGITUDINAL AXIS, A MAIN FLUIDDUCT, AND CASING MEANS FOR SAID MAIN FLUID DUCT, SAID CASING MEANSCOMPRISING FIRST AND SECOND AXIALLY SPACED SECTIONS AND AN INTERMEDIATESECTION EXTENDING BETWEEN SAID FIRST AND SECOND SECTIONS, EACH OF SAIDSECTIONS HAVING AN INNER SURFACE WHICH FORMS AN OUTER BOUNDARY WALL OF ARESPECTIVE AXIAL PORTIONS OF SAID MAIN FLUID DUCT, THE INNER SURFACE OFSAID FIRST SECTION HAVING A DOWNSTREAM END, AND THE INNER SURFACE OFSAID SECOND SECTION HAVING AN UPSTREAM END WHICH IS ALIGNED AXIALLY OFTHE COMPRESSOR WITH THE DOWNSTREAM END OF THE INNER SURFACE OF SAIDFIRST SECTION, THE INNER SURFACE OF SAID INTERMEDIATE SECTION BEINGFLUID TIGHT AND DIVERGING OUTWARDLY RELATIVELY TO THE INNER SURFACES OFTHE FIRST AND SECOND SECTIONS FROM THE DOWNSTREAM END OF THE INNERSURFACE OF SAID FIRST SECTION TOWARDS AND IN RADIALLY OUTWARDLY SPACEDRELATIONSHIP TO THE UPSTREAM END OF SAID SECOND SECTION, THE INNERSURFACE OF SAID INTERMEDIATE SECTION AND THE UPSTREAM END OF SAID SECONDSECTION DEFINING AN ANNULAR SPACE THEREBETWEEN, SAID CASING MEANS BEINGPROVIDED WITH DUCT MEANS IN FLUID FLOW COMMUNICATION WITH SAID ANNULARSPACE FOR BLEEDING COMPRESSED AIR FROM SAID MAIN FLUID DUCT, THEIMPROVEMENT COMPRISING A PLURALITY OF ANGULARLY ARRANGED STATOR BLADESPROVIDED IN SAID INTERMEDIATE SECTION, EACH OF THE STATOR BLADESCARRYING AT ITS RADIALLY OUTER END A PLATFORM FORMED INTEGRALLYTHEREWITH AND HAVING A RADIALLY INWARDLY FACING SURFACE, THE RADIALLYINWARDLY FACING SURFACE OF SAID PLATFORMS OF SAID STATOR BLADES TOGETHERFORMING SAID FLUID TIGHT INNER SURFACE OF SAID INTERMEDIATE SECTION.